wrote in message
ups.com...
Mark wrote:
Dave wrote:
Mark wrote:
modelman wrote:

Several months ago I had a high efficiency Trane XV90 natural gas
furnace and heat pump installed. Since the weather has recently been
cold enough for the gas furnace to provide heat, I have been
experiencing severe radio interference. The interference wipes out
AM
broadcast reception throughout my house. I also see snow on a TV
connected to an external antenna.

The radio noise occurs as soon as the draft inducer motor starts up;
the pitch of the interference is related to the motor speed. The
draft
inducer motor is a dc motor driven by a PWM controller on the main
circuit board. ... SNIPPED ...

DC motors are notorious noise generators. Those of us who used to be
mobile when
6 VDC was the value of a car battery, and alternators did not exist,
will attest
to the facts of generator [DC motor] noise.

A DC motor uses brushes to contact windings within the motor. As the
motor turns
the brushes continually make and break current in the rotating armature
[inductance]. This making and breaking creates a very wide HF and lower
VHF
noise spectrum. [Lots of sparks].

The solution, in the olden days, was a coaxial capacitor mounted
directly to the
frame of the motor with the DC power running through the capacitor. I
recall the
capacitor was about 1 inch in diameter and 2 inches long. Sprague made
such a
critter.

Hope this history helps.

/s/ DD, W1MCE

I'm pretty sure these motors don't have brushes and are electronically
commutated and the electronics are causing the EMI...
Mark

Hi Mark, Modern HVAC, dishwashers, washing machines,ect. use variable
speed drives, which increases the efficiency of the devices. The
increased efficiency produces increased RFI due to the switching action
of the solid state devices (SCR's, BJT's, IGBJT's.ect). My washing
machine drives me crazy on Sat. morning on HF as my maid does the
weekly wash. As for what you can do? I don't know, it would require
vast amounts of filtering at the drives, I am sure that Trane and
other mfgrs are not willing invest in.

This is completely different from the usual thermostat interference,
and will be much more difficult to get rid of.
Gary N4AST

Gentlemen Hi
and there is nothing that could be done to force OEMs
for clean up this interference (RFI?) That is nice but
you and I if interfere with some one TV in Neighborhood
FCC would be all over our ass thanks for equal justice
KA2AYS